Latex, fluid treatments for bonding, fibrous members, and composite member consisting of fiber member and vulcanized rubber members

ABSTRACT

A latex of a cyano-bearing copolymer rubber which contains units derived from an α,β-ethylenically unsaturated nitrile monomer in an amount of 10 to 30% by mass and has an iodine number of 250 or below, a Mooney viscosity (ML 1+4 , 100° C.) of 10 to 120, and a difference (ΔTg) between extrapolated glass transition initiation temperature (Tig) and extrapolated glass transition ending temperature (Teg) of 15° C. or below as determined by differential scanning calorimetry; and fluid treatments for bonding and adhesive compositions, containing the latex. The adhesive compositions are excellent in heat resistance, oil resistance, and adhesion to vulcanized rubbers, and exhibit tackiness.

TECHNICAL FIELD

The present invention relates to a fluid treatment for bonding (anadhesive treatment solution) forming an adhesive composition layerexcellent in adhesion between a fibrous member (a fiber member) and avulcanized rubber member and having sufficient tackiness, a fiber membertreated with the adhesive treatment solution, and a composite member ofthe fiber member and a vulcanized rubber member.

BACKGROUND ART

In recent years, nitrile group-containing copolymer rubber having a lowiodine value, represented by hydrogenated acrylonitrile-butadienecopolymer rubber, attracts attention. This nitrile group-containingcopolymer rubber is superior in heat resistance and oil resistance togeneral nitrile group-containing copolymer rubber having manycarbon-carbon unsaturated bonds in a main chain structure such asacrylonitrile-butadiene copolymer rubber.

An adhesive composition containing a latex of this nitrilegroup-containing copolymer rubber is excellent in heat resistance, oilresistance and adhesion to the surface of vulcanized rubber.Accordingly, it is proposed that by making a composite of a fiber membertreated with this adhesive composition and a vulcanized rubber member, amember excellent in mechanical strength is obtained (Japanese PatentApplication Laid-Open No. 8-100085). For example, when this adhesivecomposition is used in producing a belt by combining a glass core wireproduced by twisting glass fibers with a belt substrate of vulcanized,nitrile group-containing copolymer rubber, a belt having the glass corewire bonded strongly to the belt substrate can be formed.

However, this adhesive composition is poor in tackiness, and productionof a belt by using this adhesive composition is problematic. That is,the adhesive composition is poor in tackiness, and thus there is apossibility that glass fibers in the glass core wire are easily untieddue to loading applied in using the belt, and the untied brittle fibersare cut and the whole of the glass core wire is cut.

DISCLOSURE OF THE INVENTION

The object of the present invention is to provide an adhesivecomposition which is excellent in heat resistance and oil resistance, issuperior in adhesion to vulcanized rubber, and has tackiness.

The present inventors made extensive study to solve the problem, and asa result, they found that an adhesive composition prepared from a latexof nitrile group-containing copolymer rubber having a specificcomposition of the copolymer and showing a small temperature differencebetween extrapolated glass transition initiation temperature (Tig) andextrapolated glass transition end temperature (Teg) measured bydifferential scanning calorimetry is excellent in adhesiveness andstrongly bonds a fiber member to a vulcanized rubber member, and on thebasis of this finding, the present invention was completed.

According to a first aspect of the invention, there is provided a latexof nitrile group-containing copolymer rubber containing 10 to 30 mass %α,β-ethylenically unsaturated nitrile monomer unit, having an iodinevalue of 250 or less and a Mooney viscosity (ML₁₊₄, 100° C.) of 10 to120, and showing a temperature difference of 15° C. or less betweenextrapolated glass transition initiation temperature (Tig) andextrapolated glass transition end temperature (Teg) measured bydifferential scanning calorimetry. According to a second aspect of theinvention, there is provided an adhesive treatment solution comprisingthe latex and a resorcinol/formaldehyde resin. According to a thirdaspect of the invention, there is provided an adhesive compositioncomprising a resorcinol/formaldehyde resin and nitrile group-containingcopolymer rubber particles containing 10 to 30 mass % α,β-ethylenicallyunsaturated nitrile monomer unit, having an iodine value of 250 or lessand a Mooney viscosity (ML₁₊₄, 100° C.) of 10 to 120, and showing atemperature difference of 15° C. or less between extrapolated glasstransition initiation temperature (Tig) and extrapolated glasstransition end temperature (Teg) measured by differential scanningcalorimetry. According to a fourth aspect of the invention, there isprovided a fiber member comprising a layer of the adhesive compositionformed on at least a part of the surface of the fiber member. Accordingto a fifth aspect of the invention, there is provided a method ofproducing a fiber member, which comprises applying and drying theadhesive treatment solution on at least a part of the surface of a fibersubstrate. According to a sixth aspect of the invention, there isprovided a composite member comprising the fiber member bonded to avulcanized rubber member. According to a seventh aspect of theinvention, there is provided a method of producing a fibermember/vulcanized rubber composite member, which comprises bringing avulcanizing rubber composition into contact with an adhesive compositionlayer formed on the surface of a fiber member and then vulcanizing it.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the present invention is described in more detail.

The latex of the present invention is a latex of nitrilegroup-containing copolymer rubber containing 10 to 30 mass %α,β-ethylenically unsaturated nitrile monomer unit, having an iodinevalue of 250 or less and a Mooney viscosity (ML₁₊₄, 100° C.) of 10 to120, and showing a temperature difference of 15° C. or less betweenextrapolated glass transition initiation temperature (Tig) andextrapolated glass transition end temperature (Teg) measured bydifferential scanning calorimetry.

The nitrile group-containing copolymer rubber used in the presentinvention contains 10 to 30 mass % α,β-ethylenically unsaturated nitrilemonomer unit, has an iodine value of 250 or less and a Mooney viscosity(ML₁₊₄, 100° C.) of 10 to 120, and shows a temperature difference of 15°C. or less between extrapolated glass transition initiation temperature(Tig) and extrapolated glass transition end temperature (Teg) measuredby differential scanning calorimetry.

The α,β-ethylenically unsaturated nitrile monomer includesacrylonitrile, α-halogenoacrylonitrile such as α-chloroacrylonitrile andα-bromoacrylonitrile, and α-alkylacrylonitrile such as methacrylonitrileand ethacrylonitrile, among which acrylonitrile is preferable.

The content of the α,β-ethylenically unsaturated nitrile monomer unit(referred to hereinafter as monomer unit (a)) in the nitrilegroup-containing copolymer rubber is 10 to 30 mass %, preferably 12 to25 mass %, more preferably 17 to 23 mass %. When the content of themonomer unit (a) is too low, the resulting adhesive composition isinferior in adhesiveness, while when the content is too high, thecomposition is inferior in tackiness.

In production of the nitrile group-containing copolymer rubber, amonomer copolymerizable with the α,β-ethylenically unsaturated nitrilemonomer is exemplified by a conjugated diene monomer, anon-conjugateddiene monomer and α-olefin. The conjugated diene monomer includes, forexample, 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene,1,3-pentadiene etc., among which 1,3-butadiene is preferable. Thenon-conjugated diene monomer is preferably the one having 5 to 12 carbonatoms, and examples include 1,4-pentadiene, 1,4-hexadiene,vinylnorbornene, dicyclopentadiene etc. The α-olefin is preferably theone having 2 to 12 carbon atoms, and examples include ethylene,propylene, 1-butene, 4-methyl-1-pentene, 1-hexene, 1-octene etc. Themonomer unit (a) may also be copolymerized with an aromatic vinylmonomer, a fluorine-containing vinyl monomer, an α,β-ethylenicallyunsaturated monocarboxylic acid, an α,β-ethylenically unsaturateddicarboxylic acid or an anhydride thereof, a copolymerizable aginginhibitor etc.

The aromatic vinyl monomer includes, for example, styrene,α-methylstyrene, vinylpyridine etc. The fluorine-containing vinylmonomer includes, for example, fluoroethyl vinyl ether, fluoropropylvinyl ether, o-trifluoromethyl styrene, vinyl pentafluorobenzoate,difluoroethylene, tetrafluoroethylene etc. The α,β-ethylenicallyunsaturated monocarboxylic acid includes, for example, acrylic acid,methacrylic acid etc. The α,β-ethylenically unsaturated dicarboxylicacid includes, for example, itaconic acid, fumaric acid, maleic acidetc. The α,β-ethylenically unsaturated dicarboxylic anhydride includes,for example, itaconic anhydride, maleic anhydride etc. Thecopolymerizable aging inhibitor includes, for example,N-(4-anilinophenyl)acrylamide, N-(4-anilinophenyl)methacrylamide,N-(4-anilinophenyl)cinnamamide, N-(4-anilinophenyl)crotonamide,N-phenyl-4-(3-vinylbenzyloxy)aniline,N-phenyl-4-(4-vinylbenzyloxy)aniline etc.

The iodine value of the nitrile group-containing copolymer rubber of thepresent invention is 250 or less, preferably 200 or less, morepreferably 180 or less. When the iodine value is too high, the adhesivecomposition is inferior in heat resistance.

The Mooney viscosity (ML₁₊₄, 100° C.) of the nitrile group-containingcopolymer rubber of the present invention is 100 to 120, preferably 15to 80, more preferably 20 to 60. When the Mooney viscosity is too low,the adhesive composition may be inferior in mechanical strength, whilewhen the Mooney viscosity is too high, the composition may be inferiorin tackiness.

The temperature difference (ΔTg) between the extrapolated glasstransition initiation temperature (Tig) and extrapolated glasstransition end temperature (Teg) of the nitrile group-containingcopolymer rubber of the present invention, as determined by differentialscanning calorimetry prescribed in JIS K7121 (Method of MeasuringTransition Temperature of Plastics), is 15° C. or less, preferably 14°C. or less, more preferably 13° C. or less. When this temperaturedifference (ΔTg) is too great, the adhesive composition of the presentinvention is inferior in tackiness.

To allow the temperature difference (ΔTg) between the extrapolated glasstransition initiation temperature (Tig) and the extrapolated glasstransition end temperature (Teg) to be in the above range, thecompositional distribution breadth of the monomer unit (a) in thenitrile group-containing copolymer rubber and the compositionaldistribution breadth of the monomer unit (referred to hereinafter asmonomer (b)) copolymerizable with the α,β-ethylenically unsaturatednitrile monomer is preferably 80 mass % or less, more preferably 70 mass% or less, still more preferably 55 mass % or less. The compositionaldistribution breadth of each monomer refers to the ratio of [differencebetween the maximum and minimum contents of each monomer in a minutepart of the polymer] to [content of each monomer in the whole polymer].The minute part of the polymer refers to a very small part of thepolymer, and refers to a part accounting for preferably 1 to 5 mass %,more preferably 2 to 4 mass %, of the molecular weight of the polymer.The compositional distribution breadth is determined usually based onmeasurements of a change with time in the amount of the unreactedmonomer in the polymerization reaction. When the compositionaldistribution breadth is too broad, the temperature difference (ΔTg) maybe too great.

The structure of the monomer unit may be changed by treatment such ashydrogenation after the completion of polymerization. In this case, thecompositional distribution breadth shall be in the above range, assumingthat the monomer unit before and after change is the same monomer unit.For example, when butadiene is copolymerized and hydrogenated after thecompletion of copolymerization, at least a part of unsaturated bonds ofbutadiene units are hydrogenated to form saturated butadiene units. Inthis case, it is assumed that the saturated butadiene unit is the sameas the butadiene unit, and the compositional distribution breadth of thetwo kinds of units in total shall be in the above range.

When plural kinds of monomers are used as the monomer copolymerizablewith the α,β-ethylenically unsaturated nitrile monomer, thecompositional distribution breadth of the respective monomers ispreferably in the above range. When plural kinds of monomers are used asthe α,β-ethylenically unsaturated nitrile monomer, the compositionaldistribution breadth of the respective monomers is also preferably inthe above range.

The content of the monomer unit (a) or (b) in the nitrilegroup-containing copolymer rubber can be determined by a combination ofa plurality of measurement methods such as nitrogen content measurementby a semimicro-Kjeldahl method, measurement of the amount of unsaturatedbonds by analysis of IR absorption spectrum or measurement of iodinevalue, identification of a partial structure by analysis of IRabsorption spectrum, ¹H-NMR, ¹³C-NMR, pyrolysis gas chromatography etc.,and measurement of amount ratio. Generally, the identification of apartial structure and measurement of amount ratio by ¹H-NMR are the mostreliable, but there is the case where analysis is not feasible becauseof overlapping of a plurality of peaks in ¹H-NMR chart, and it is thusdesired in analysis to use ¹H-NMR in combination with other methods.

In the latex of the present invention, the nitrile group-containingcopolymer rubber exists as particles, and the average diameter of theparticles is preferably 50 to 150 μm, more preferably 70 to 120 μm,still more preferably 80 to 100 μm. When the particle diameter is toosmall, the particles are easily aggregated, while when the particlediameter is too large, the particles are precipitated, thus makingstorage thereof or preparation of the adhesive treatment solutiondifficult.

The method of producing the latex according to the present invention isnot particularly limited, but usually emulsion polymerization is used.Polymerization assistants used generally in emulsion polymerization,such as an emulsifying agent, a polymerization initiator and amolecular-weight regulator, may be used. The type and amount of theseadditives are not particularly limited insofar as the nitrilegroup-containing copolymer rubber latex can be obtained.

When the latex of the present invention is to be produced by emulsionpolymerization, the compositional distribution breadth of the monomerunit is regulated so as to be in the specific range duringpolymerization as described above, to polymerize rubber whoseextrapolated glass transition initiation temperature (Tig) andextrapolated glass transition end temperature (Teg) show a temperaturedifference (ΔTg) in the above-defined range. The polymerization reactionconditions for regulating the compositional distribution breadth may bepreviously determined by a preliminary experiment. In the preliminaryexperiment, the amount of each monomer in the polymerization reactionsolution is measured as the polymerization proceeds, preferably everytime the degree of polymerization conversion is increased by 1 to 5 mass%, more preferably every time the degree of polymerization conversion isincreased by 2 to 4 mass %, whereby the content of each monomer in aminute part of the polymer is determined. The polymerization reactionconditions are determined such that the compositional distributionbreadth determined on the basis of the content comes to be in the rangedescribed above. Generally, the compositional distribution breadth iscontrolled by additionally adding a specific amount of each monomer at apredetermined point in time. Examination of the polymerization reactionconditions can also be made by computer simulation etc., and its resultmay be confirmed in the experiment.

To allow the iodine value of the polymerized rubber to be 250 or less,hydrogenation reaction is necessary. For this reaction, a hydrogenationcatalyst may be added in a necessary amount to an aqueous emulsifyingagent solution having the rubber particles dispersed therein, followedby bringing the rubber particles in the aqueous emulsifying agentsolution into contact with hydrogen. The hydrogenation catalyst is notparticularly limited. The hydrogenation catalyst can be used as asupported catalyst having a catalytic component supported on a carrierand introduced into a reaction system. The hydrogenation catalyst canalso be used as a non-supported catalyst which without supporting acatalytic component on a carrier, is dissolved or dispersed directly ina reaction system. Further, the supported and non-supported catalystscan be simultaneously used. The hydrogenation temperature is preferably20 to 150° C., more preferably 30 to 100° C. When the hydrogenationtemperature is too low, the reaction rate may be low, while when thetemperature is too high, side reactions such as hydrogenation of nitrilegroup may occur. A hydrogen gas is used as the hydrogen source and maybe brought into contact with the nitrile group-containing unsaturatedcopolymer rubber in latex form. The hydrogen pressure is preferablyatmospheric pressure to 150 kg/cm², more preferably 5 to 100 kg/cm².When the hydrogen pressure is too low, the reaction rate may be low,while when the hydrogen pressure is too high, the safety of facilitiesetc. may be problematic. After the hydrogenation reaction is finished,the hydrogenation catalyst is preferably removed, but if its amount isin such a range as not to influence tackiness, the catalyst may remain.The method of removing the hydrogenation catalyst is not particularlylimited, and for example, the hydrogenation catalyst may be removed bybringing the reaction mixture into contact with ion-exchange resin toadsorb it onto the resin.

The solids content of the latex of the present invention is preferably10 to 60 mass %, more preferably 20 to 50 mass %, still more preferably35 to 45 mass %. When the solids content is too low, a uniform adhesivetreatment solution may not be prepared, while when it is too high, thecomposition may be inferior in shelf stability.

The adhesive treatment solution of the present invention comprises thelatex and a resorcinol/formaldehyde resin. The adhesive treatmentsolution is the one wherein the components in the adhesive compositionfor bonding a pair of substrates to each other in a composite materialare dispersed in an aqueous medium.

The resorcinol/formaldehyde resin used in the present invention is aresin obtained by reacting resorcinol with formaldehyde. It may be anovolak type or resol type, and the amount of formaldehyde reacting with1 mole of resorcinol is preferably 0.1 to 3.5 moles, more preferably 0.2to 3 moles. The reaction method is not particularly limited, and thereaction may be carried out by a known method.

The amount of the resorcinol/formaldehyde resin blended with 100 partsby weight of the nitrile group-containing copolymer rubber particlesdispersed in the latex is preferably 3 to 60 parts by weight, morepreferably 5 to 40 parts by weight, still more preferably 10 to 30 partsby weight. When the amount of the resorcinol/formaldehyde resin blendedis too low, the adhesive composition may be poor in adhesiveness, whilewhen the amount is too high, the adhesive composition may be poor intackiness.

The adhesive composition of the present invention comprises aresorcinol/formaldehyde resin and nitrile group-containing copolymerrubber particles containing 10 to 30 mass % α,β-ethylenicallyunsaturated nitrile monomer unit, having an iodine value of 250 or lessand a Mooney viscosity of 10 to 120, and showing a temperaturedifference of 15° C. or less between extrapolated glass transitioninitiation temperature (Tig) and extrapolated glass transition endtemperature (Teg) measured by differential scanning calorimetry.

The type of the nitrile group-containing copolymer rubber particles andthe resorcinol/formaldehyde resin and the ratio of the two are the sameas in the latex and the adhesive treatment solution described above.

The water content in the adhesive composition is preferably 1 mass % orless, more preferably 0.5 mass % or less, more preferably 0.1 mass % orless. When the water content is too high, the adhesiveness and tackinessmay be lowered. After adhesion, the water may cause foaming and releaseof the adhesive-bonded substrate.

The method of producing the adhesive composition is not particularlylimited, but generally the adhesive composition is produced by removingwater from the adhesive treatment solution: specifically, a coating filmformed by applying the adhesive treatment solution onto the surface ofat least one of a pair of substrates intended to be adhesive-bonded andthen drying the solution is used as an adhesive composition layer. Thecoating method is not particularly limited, and may be carried out bybrushing, spraying or dipping. The method of drying water is notparticularly limited, and the adhesive treatment solution may be treatedby a combination of reduced pressure and heating.

The thickness of the adhesive composition layer is not particularlylimited. For example, when the adhesive composition is applied to aglass fiber strand of about 0.1mm in thickness, the thickness of thecomposition after drying is preferably 0.1 to 10 μm, more preferably 0.2to 5 μm, still more preferably 0.5 to 2 μm. A too thick layer is notpreferable because the strength of a glass fiber cord obtained bytwisting the strands is adversely influenced. On the other hand, whenthe adhesive composition layer is to be formed by a method of sprayingor dipping a woven or nonwoven fabric, the thickness of the compositionafter drying is preferably 0.1 to 100 μm, more preferably 0.5 to 100 μm,still more preferably 1 to 50 μm.

Preferable examples of one substrate out of a pair of substrates to beadhesive-bonded to each other include fiber substrates, and reinforcingfiber substrates such as a nonwoven fabric formed from fibers, a threadhaving fibers twisted therein, a fabric having such threads woventherein, and a cord having fibers twisted therein are preferable.Preferable fibers include glass fiber, polyester fiber, polyamide fiber,polybenzobisoxazole fiber etc.

The fiber member of the present invention has a layer of the adhesivecomposition formed on at least a part of the surface of a fibersubstrate. When the fiber substrate is a thread or cord, the adhesivecomposition layer may be formed on the surface of a thread or cordobtained by twisting fibers to form the fiber member, or a fiber or astrand of bundled fibers may be coated thereon with the adhesivetreatment solution to form a layer of the adhesive composition and thentwisted to give a thread or cord used as the fiber member. A wovenfabric using the threads obtained in this manner may be used as thefiber member.

Particularly in the fiber member made of a thread or cord produced bytwisting fibers having the adhesive composition layer formed thereon,the twisted fibers are hardly frayed, and even if the fibers in thetwisted thread or cord are partially cut, such cutting hardly causesfray. This is preferable in that the strength of the fiber member can bemaintained by preventing fray.

The surface of the formed layer of the adhesive composition is excellentin adhesion to a vulcanized rubber member. In particular, the adhesivecomposition layer while being into contact with a vulcanizable rubbercomposition is vulcanized, whereby the fiber member and the vulcanizedrubber member can be strongly bonded to each other.

The method of producing the fiber member is not particularly limited,but a method that involves applying the adhesive treatment solution ontoat least a part of the surface of a fiber member and then drying it isgenerally used.

Preferable examples of the other substrate out of a pair of substratesintended to be adhesive-bonded include vulcanized rubber members such asbelt, tire and hose. Non-vulcanized rubber serving as the startingmaterial thereof is not particularly limited, but preferable rubberincludes nitrile group-containing copolymer rubber, and particularlypreferable rubber includes nitrile group-containing copolymer rubberhaving an iodine value of 100 or less. The non-vulcanized rubber may becompounded if necessary with general additives such as reinforcingmaterials such as silica, carbon etc., fillers such as talc, clay etc.,stabilizers such as an antioxidant, a weathering agent etc., andpigments. By compounding the non-vulcanized rubber with a vulcanizingagent suitable for the characteristics of the rubber, a vulcanizablerubber composition is prepared and then vulcanized to give a vulcanizedrubber member. In the case of the nitrile group-containing copolymerrubber, sulfur, a sulfur-based vulcanizing agent such as morpholinedisulfide, or an organic peroxide vulcanizing agent is generally used.

The composite member of the present invention comprises a fiber memberadhesive-bonded to a vulcanized rubber member. The method of producingthe composite member is not particularly limited, but a method thatinvolves bringing an adhesive composition layer formed on the surface ofa fiber member into contact with a vulcanizable rubber composition andthen vulcanizing the vulcanizable rubber composition is preferably used.According to this method, a composite member having the fiber memberbonded strongly to the vulcanized rubber member can be obtained.

The method of bringing the adhesive composition layer formed on thesurface of a fiber member into contact with a vulcanizable rubbercomposition is not particularly limited. Depending on the object, atwo-layer structure of the fiber member and the vulcanizable rubbercomposition may be formed, or the fiber member may be buried in thevulcanizable rubber composition. Molding and vulcanization may besimultaneously conducted; molding may be followed by vulcanization; orafter vulcanization, the composite member may be cut and molded. Forexample, the fiber member and the vulcanizable rubber composition can befixed respectively in predetermined positions in a mold, whereby theadhesive composition layer is brought into contact with the vulcanizablerubber composition, and the mold can be heated to effect molding andvulcanization simultaneously. Alternatively, the fiber member may belaminated on the vulcanizable rubber composition in plate formpreviously subjected to extrusion molding, whereby the layer of theadhesive composition is brought into contact with the vulcanizablerubber composition, followed by vulcanization by heating.

EXAMPLES

Hereinafter, the present invention is described in more detail byreference to the Examples. Unless otherwise specified, “parts” refer toparts by weight.

The content of each monomer unit in the nitrile group-containingcopolymer rubber is a value determined on the basis of ¹H-NMR, iodinecontent measurement, and nitrogen content measurement by thesemimicro-Kjeldahl method. It was confirmed that this value does notcontradict a difference between the amount of the monomer used inpolymerization and the amount of the remaining monomer.

The extrapolated glass transition initiation temperature (Tig) andextrapolated glass transition end temperature (Teg) were measured byheat reflux differential scanning calorimetry according to JIS K7121.However, the rate of heating was changed from 20° C./min. to 10° C./min.in measurement in order to measurement accuracy.

The iodine value and Mooney viscosity (ML₁₊₄, 100° C.) were measuredaccording to JIS K 6235 and JIS K 6300, respectively.

The adhesion of a glass fiber cord to a vulcanized rubber was measuredby a method described later according to JIS K 3256.

The tackiness between glass and the adhesive composition was measured byusing a Tel-Tack meter (model TT-1 manufactured by Monsanto, JP-B47-12830)

Reference Example 1

Palladium nitrate (manufactured by NE Chemcat Corporation) was dissolvedat a palladium concentration of 10 mass % in distilled water to prepare100 ml aqueous solution of palladium nitrate. While the pH of thisaqueous solution was monitored, the pH was adjusted to 12 by addingsodium hydroxide (solid). 20 ml of this aqueous basic solution was mixedwith 1L separately prepared carrier slurry (carrier: magnesium silicatemanufactured by Tomita Pharmaceutical Co., Ltd.; the amount of thecarrier in the slurry: 100 g). The pH of the slurry after being mixedwas 12. The mixture was stirred for 30 minutes, and then solids wereseparated by filtration and washed sufficiently with distilled water.The recovered solids were vacuum-dried at 60° C. for 20 hours to give asupported catalyst. The amount of palladium supported thereon, asdetermined by the atomic-absorption method, was 2 mass %.

Example 1

A reactor was charged with an emulsifying agent consisting of 205 partsof deionized water and 3 parts of sodium dodecyl sulfate (emulsifyingagent), and then 11 parts of acrylonitrile, 89 parts of 1,3-butadiene,0.54 part of t-dodecyl mercaptan (molecular-weight regulator), 0.015part of ferrous sulfate (activator) and 0.043 part of p-menthanehydroperoxide (polymerization initiator) were added thereto, and whilethe degree of polymerization conversion was measured, the emulsionpolymerization of the mixture was initiated at 10° C. When the degree ofpolymerization conversion reached 26%, 4.3 parts of acrylonitrile wereadded. When the degree of polymerization conversion reached 41% uponadding the added acrylonitrile to a criterion for calculating the degreeof polymerization conversion, 4.3 parts of acrylonitrile were furtheradded. When the degree of polymerization conversion reached 59% uponadding this additionally added acrylonitrile to a criterion forcalculating the degree of polymerization conversion, 4.3 parts ofacrylonitrile were added again. When the degree of polymerizationconversion reached 80% upon adding this additionally added acrylonitrileto a criterion for calculating the degree of polymerization conversion,0.129 part of hydroxylamine sulfate was added to terminate thepolymerization. During the polymerization, a very small amount of thepolymerization reaction solution was collected and analyzed every timethe degree of polymerization conversion was increased by 3%, and thecontent of each monomer in a minute part of the polymer was determined.The results are shown in Table 1. Following termination of thepolymerization, the reaction solution was heated, and the unreactedmonomer was recovered by steam distillation at 70° C. under reducedpressure, and then 2 parts of 2,6-di-tert-butyl-4-methyl phenol (aginginhibitor) were added to the reaction mixture, whereby a nitrilegroup-containing copolymer rubber latex was obtained. The content ofacrylonitrile in the nitrile group-containing copolymer rubber containedin this latex was 22.5%, the iodine value was about 364, the Mooneyviscosity (ML₁₊₄, 100° C.) was 30, and ΔTg was 13° C.

The hydrogenation catalyst obtained in Reference Example 1 was added tothe nitrile group-containing copolymer rubber latex such that the amountof the palladium became 1600 ppm, and the latex was hydrogenated at 50°C. by blowing a hydrogen gas at a hydrogen pressure of 5 MPa until theiodine value reached 160, to give a hydrogenated nitrilegroup-containing copolymer rubber latex. The content of acrylonitrile inthe nitrile group-containing copolymer rubber contained in this latexwas 22.5%, the Mooney viscosity (ML₁₊₄, 100° C.) was 30, and ΔTg was 13°C.

To the resulting hydrogenated nitrile group-containing copolymer rubberlatex was added a resorcinol/formaldehyde resin (reaction product of 1mol resorcinol and 1 mol formaldehyde, manufactured by Wako PureChemical Industries) in an amount of 20 parts relative to 100 parts ofthe rubber particles, and the mixture was stirred slowly until it becameuniform, whereby an adhesive treatment solution was prepared.

This adhesive treatment solution was applied onto each of glass fiberstrands (filament diameter, 9 μm; 101 Tex (number of filaments, 600))having a non-alkali glass composition (SiO₂, 64.4%; Al₂O₃, 25%; CaO,0.3%; MgO 10.0%; B₂O₃, 0.1%; Na₂O and K₂O in total, 0.2%) such that thethickness of the adhesive composition layer became about 1.5 μm, and thestrands were heat-treated at 280° C. for 1 minute and then subjected topreliminary twisting 2.1 times per inch, and 11 strands were combinedand subjected to final twisting 2.1 times per inch in the oppositedirection to the preliminary twisting, to give a glass fiber cord.

60 parts of carbon black N550, 5 parts of zinc white No. 1, 1 part ofstearic acid, 10 parts of trioctyl trimellitate, 1.5 parts of4,4-(α,α-dimethylbenzyl)diphenylamine, 1.5 parts ofmercaptobenzothiazole zinc salt, 1.5 parts of tetramethyl thiuramdisulfide, 0.5 part of sulfur and 1 part of cyclohexyl benzothiazylsulfonamide were incorporated into 100 parts of hydrogenatedacrylonitrile/butadiene copolymer rubber (Zet Pole 2020 manufactured byNippon Zeon Co., Ltd.; acrylonitrile unit content, 36.2%; iodine value28; Mooney viscosity (ML₁₊₄, 100° C.) 78), to prepare a vulcanizablerubber composition. This vulcanizable rubber composition was molded intoa sheet of 5 mm in thickness by a press pressure of 5 MPa.

The above glass fiber cords were arranged in a size of 12 cm in lengthand 25 mm in width on the sheet molding of the vulcanizable rubbercomposition and then vulcanized at 150° C. for 30 minutes at a presspressure of 5 MPa to give an adhesion test specimen. The resulting testspecimen was measured for the initial adhesion between the glass fibercord and the vulcanized rubber in a peel test according to JIS K 6256.The content of the glass fiber cord in the test specimen was about 30mass %.

The resulting adhesive treatment solution was used to measure thetackiness between glass and the adhesive composition. The results areshown in Table 1.

Comparative Example 1

A nitrile group-containing copolymer rubber latex was obtained bypolymerization in the same manner as in Example 1 except that uponinitiation of polymerization, the amount of acrylonitrile was changedfrom 11 parts to 20 parts, the amount of 1,3-butadiene was changed from89 parts to 80 parts, and during the polymerization, no additionalacrylonitrile was added. The content of acrylonitrile in the nitrilegroup-containing copolymer rubber contained in this latex was 22.9%, theiodine value was about 360, the Mooney viscosity (ML₁₊₄, 100° C.) was30, and ΔTg was 44° C. This latex was hydrogenated in the same manner asin Example 1 to give hydrogenated nitrile group-containing copolymerrubber latex. The content of acrylonitrile in the hydrogenated nitrilegroup-containing copolymer rubber contained in this latex was 22.9%, theiodine value was about 160, the Mooney viscosity (ML₁₊₄, 100° C.) was30, and ΔTg was 42° C. Using this hydrogenated nitrile group-containingcopolymer rubber latex, an adhesive treatment solution and an adhesiontest specimen were obtained in the same manner as in Example 1, and theinitial adhesion between the glass fiber cord and the vulcanized rubberand the tackiness between glass and the adhesive composition weremeasured. The results are shown in Table 1.

Comparative Example 2

A nitrile group-containing copolymer rubber latex was obtained bypolymerization in the same manner as in Example 1 except that the amountof t-dodecylmercaptan was changed from 0.54 part to 0.05 part. Thecontent of acrylonitrile in the nitrile group-containing copolymerrubber contained in this latex was 22.5%, the iodine value was about364, the Mooney viscosity (ML₁₊₄, 100° C.) was 155, and ΔTg was 13° C.This latex was hydrogenated in the same manner as in Example 1 to givehydrogenated nitrile group-containing copolymer rubber latex. Thecontent of acrylonitrile in the hydrogenated nitrile group-containingcopolymer rubber contained in this latex was 22.5, the iodine value was160, the Mooney viscosity (ML₁₊₄, 100° C.) was 150, and ΔTg was 13° C.Using this hydrogenated nitrile group-containing copolymer rubber latex,an adhesive treatment solution and an adhesion test specimen wereobtained in the same manner as in Example 1, and the initial adhesionbetween the glass fiber cord and the vulcanized rubber and the tackinessbetween glass and the adhesive composition were measured. The resultsare shown in Table 1.

Comparative Example 3

The same treatment as in Example 1 was carried out except that thenitrile group-containing copolymer rubber latex before hydrogenation wasused in place of the hydrogenated nitrile group-containing copolymerrubber latex. The results are shown in Table 1. The content ofacrylonitrile in the nitrile group-containing copolymer rubber containedin this latex was 22.5%, the iodine value was about 364, the Mooneyviscosity (ML₁₊₄, 100° C.) was 30, and ΔTg was 13° C. TABLE 1 ExampleComparative Example 1 1 2 3 Nitrile group-containing copolymer rubberAcrylonitrile unit (a) 22.5 22.9 22.5 22.5 Content (mass%) Maximumcontent in minute part 27.9 33.6 27.9 27.9 (mass%) Minimum content inminute part 17.4 9.6 17.4 17.4 (mass%) Compositional distributionbreadth 47 105 47 47 (mass%) Butadiene unit (b) (before 77.5 77.1 77.577.5 hydrogenation Content (mass%) Maximum content in minute part 82.690.4 82.6 82.6 (mass%) Minimum content in minute part 72.1 66.4 72.172.1 (mass%) Compositional distribution breadth 13 31 13 13 (mass%)Extrapolated glass transition initiation −53 −70 −53 −53 temperature(Tig) (° C.) Extrapolated glass transition end −40 −28 −40 −40temperature (Teg) (° C.) Difference (TgΔ) between Tig and 13 42 13 13Teg (° C.) Mooney viscosity 30 30 150 30 Iodine value 160 160 160 400Tackiness between glass and adhesive 6.78 3.34 2.22 4.47 composition(×10⁵ Pa) Adhesion between glass fiber cord 8.66 7.87 8.27 9.45 andvulcanized rubber (×10³ N/m)

Composite members prepared by using adhesive treatment solutions whosenitrile-containing copolymer rubber latex had a too large differencebetween extrapolated glass transition initiation temperature (Tig) andextrapolated glass transition end temperature (Teg) (Comparative Example1), too high Mooney viscosity (Comparative Example 2) or too high iodinevalue (Comparative Example 3) were inferior in tackiness between thefiber member and the adhesive composition layer.

On the other hand, when the latex of the present invention was used, thecomposite member was excellent not only in adhesion between the glassfiber cord and the vulcanized rubber but also in tackiness.

INDUSTRIAL APPLICABILITY

The adhesive composition of the present invention is excellent not onlyin adhesion to nitrile group-containing copolymer rubber having a lowiodine value but also in tackiness. Because of excellent tackiness, theadhesive composition can bundle fibers strongly and prevents thedeterioration of a reinforcing fiber substrate caused by fraying andcutting of fibers. Accordingly, the adhesive composition of the presentinvention can be used in production of fiber-reinforced belts, tires andhoses.

1. A latex of nitrile group-containing copolymer rubber containing 10 to30 mass % α,β-ethylenically unsaturated nitrile monomer unit, having aniodine value of 250 or less and a Mooney viscosity (ML₁₊₄, 100° C.) of10 to 120, and showing a temperature difference (ΔTg) of 15° C. or lessbetween extrapolated glass transition initiation temperature (Tig) andextrapolated glass transition end temperature (Teg) measured bydifferential scanning calorimetry.
 2. The latex according to claim 1,wherein the temperature difference (ΔTg) is 14° C. or less.
 3. The latexaccording to claim 1 or 2, wherein the compositional distributionbreadth of each monomer unit in the nitrile group-containing copolymerrubber is 80 mass % or less wherein the compositional distributionbreadth of each monomer is the ratio of a difference between the maximumand minimum contents of each monomer in a minute part of the polymer tothe content of each monomer in the whole polymer.
 4. The latex accordingto claim 1, wherein the compositional distribution breadth of a monomerunit copolymerizable with the α,β-ethylenically unsaturated nitrilemonomer is 80 mass % or less wherein the compositional distributionbreadth of each monomer is the ratio of a difference between the maximumand minimum contents of each monomer in a minute part of the polymer tothe content of each monomer in the whole polymer.
 5. The latex accordingto claim 1, wherein the content of the α,β-ethylenically unsaturatednitrile monomer unit in the nitrile group-containing copolymer rubber is12 to 25 mass %.
 6. The latex according to claim 1, wherein the iodinevalue of the nitrile group-containing copolymer rubber is 200 or less.7. The latex according to claim 1, wherein the average particle diameterof the nitrile group-containing copolymer rubber is 50 to 150 μm.
 8. Anadhesive treatment solution comprising the latex according to claim 1and a resorcinol/formaldehyde resin.
 9. The treatment solution accordingto claim 8, wherein the amount of the resorcinol/formaldehyde resinincorporated into 100 parts by weight of the nitrile group-containingcopolymer rubber dispersed in the latex is 3 to 60 parts by weight. 10.An adhesive composition comprising a resorcinol/formaldehyde resin andnitrile group-containing copolymer rubber particles containing 10 to 30mass % α,β-ethylenically unsaturated nitrile monomer unit, having aniodine value of 250 or less and a Mooney viscosity (ML₁₊₄, 100° C.) of10 to 120, and showing a temperature difference (ΔTg) of 15° C. or lessbetween extrapolated glass transition initiation temperature (Tig) andextrapolated glass transition end temperature (Teg) measured bydifferential scanning calorimetry.
 11. The adhesive compositionaccording to claim 10, wherein the amount of the resorcinol/formaldehyderesin incorporated into 100 parts by weight of the nitrilegroup-containing copolymer rubber particles is 3 to 60 parts by weight.12. The adhesive composition according to claim 10 or 11, wherein thewater content in the composition is 1 mass % or less.
 13. A fiber membercomprising a layer of the adhesive composition according to claim 10formed on at least a part of the surface of a fiber member.
 14. Thefiber member according to claim 13, wherein the thickness of theadhesive composition layer after drying is 0.1 to 10 μm.
 15. The fibermember according to claim 13, wherein the fiber constituting the fibersubstrate is selected from the group consisting of glass fiber,polyester fiber, polyamide fiber and polybenzobisoxazole.
 16. A methodof producing a fiber member, which comprises applying and drying theadhesive treatment solution according to claim 8 on at least a part ofthe surface of a fiber substrate.
 17. A composite member comprising thefiber member according to claim 13 adhesive-bonded to a vulcanizedrubber member.
 18. A method of producing a fiber member/vulcanizedrubber composite member, which comprises bringing a vulcanizable rubbercomposition into contact with an adhesive composition layer formed onthe surface of the fiber member according to claim 13 and thenvulcanizing it.